Homework Help: Pressure vessels, wall thickness

1. Dec 4, 2013

Big Jock

20 m3 of gas at a pressure of 25 bar is to be stored in a cylindrical
pressure vessel 2 m long. Given the following information :
The yield strength of the vessel material is 14,000 psi
If a factor of safety of 5 is to be used, determine:

(a) Whether the vessel should be treated as a thin or thick cylinder.
(b) The wall thickness required for the pressure vessel

The information I have gathered to date is

14,000psi= 14,000 / 0.14503773773=9.6526602 x 10^6 Pa
20m^3=20,000Litres
Pressure of gas=25bars-2500kpa=2.5 x 10^6
V=∏r^2h
r=√v/∏h=1.784 Metres
D=2r=3.568 Metres

These are all the values I have at the moment. Hopefully as I continue to try and solve it solve kind soul may see this post and give me a nudge in the right direction. Many thanks in advance....

2. Dec 4, 2013

Big Jock

Hoop stress= yield strength / safety factor = 19.3 x 10^6
thickness= pr/hoop stress = 0.231m =231mm
so I conclude that the cylinder is thick walled and is a 7.222
and the minimum wall thickness must be 231mm

Could someone tell if this is correct and answers the questions suitably please